Conventionally, a nonaqueous electrolyte secondary battery has been known that includes a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator.
Known as this kind of battery is a battery that includes a positive electrode having: a positive current collector; and a positive composite layer that is formed on the positive current collector and contains a positive active material, the positive current collector being formed of a metal foil and a conductive layer that is formed on a surface of the metal foil and contains carbon fine particles (for example, Patent Document 1). In the battery disclosed in Patent Document 1, the porosity of the positive composite layer is 25 to 40% and the average particle diameter of the positive active material is 10 μm or less.
The battery disclosed in Patent Document 1 sometimes decreases power by repetitive charge-discharge in a high-temperature environment.